Title:
FLASH DEVICE
United States Patent 3859562
Abstract:
A flash device which can illuminate even when a terminal voltage of a main capacitor incorporated therein is lower than the lowest voltage enabling discharge of a flash discharge tube, which comprises a power source, a main capacitor which is charged by said power source, a flash discharge tube which is provided in the discharge circuit of the main capacitor and is given the voltage charged across the main capacitor, a triggering circuit including a synchronizing contact for illuminating the flash discharge tube, and means for giving additional voltage to the flash discharge tube, said means being connected to the flash discharge tube.
US Patent References:
ELECTRIC SYSTEM FOR FIRING A GASEOUS DISCHARGE DEVICE
Cadwallader - November 1971 - 3624445
ELECTRONIC FLASH CIRCUITS
Tadokoro - December 1973 - 3781602
ELECTRIC SYSTEM FOR FIRING A GASEOUS DISCHARGE DEVICE
Cadwallader - November 1971 - 3624445
ELECTRONIC FLASH CIRCUITS
Tadokoro - December 1973 - 3781602
Application Number:
05/264714
Publication Date:
01/07/1975
Filing Date:
06/21/1972
View Patent Images:
Export Citation:
Assignee:
Canon Kabushiki Kaisha (Tokyo, JA)
Primary Class:
Other Classes:
315/241R, 315/276
International Classes:
G03B15/05; H05B41/32; H05B41/30; H05B37/00
Field of Search:
315/241P,241R,276,277,289
Primary Examiner:
Smith, Alfred E.
Assistant Examiner:
Dahl, Lawrence J.
Attorney, Agent or Firm:
Toren, And Mcgeady
Claims:
What is claimed is
1. A flash device, comprising a power source, a main capacitor charged by said power source, a discharge circuit for said main capacitor, a flash discharge tube which is provided in the discharge circuit, said discharge tube having a trigger electrode for triggering discharge, a diode in said discharge circuit, a transformer having a primary winding and having a secondary winding connected in series with the diode in the discharge circuit, a synchronizing contact switch connected to the primary winding for triggering said discharge tube, trigger means having a trigger capacitor and a trigger coil coupled with the trigger electrode, and an auxiliary capacitor connected in parallel with said diode and the secondary winding for charging during trigger operation to add to the magnitude of the voltage applied by said main capacitor to the discharge tube and for discharging during discharge of the discharge tube.
2. A flash device as in claim 1, wherein said trigger coil includes a primary winding and said synchronizing contact is connected in both the primary winding of the trigger coil and the primary winding of the transformer.
3. A discharge system for operating a flash unit from a power source, comprising discharge capacitor means for coupling across the power source, circuit means for coupling said capacitor means across the flash unit and for applying the voltage appearing at said capacitor means across the unit, triggering means to be coupled to said flash unit for applying a trigger pulse to the flash unit, said circuit means including a capacitor to be connected in series with the flash unit and control means coupled to said trigger means for charging the capacitor with a voltage that increases the magnitude of the voltage applied by said capacitor means across the unit, said control means including a path means for forming a discharge path for current through the unit, said path means including a diode.
4. A system as in claim 3, wherein the diode is poled for discharging current from said capacitor means when the flash unit discharges.
5. A system as in claim 3, wherein said control means includes a transformer coupled to said triggering means.
6. A system as in claim 3, wherein said control means includes a transformer coupled to said triggering means and said transformer has a secondary winding forming a part of said path means.
7. A system as in claim 6, wherein said path means includes a diode.
8. A system as in claim 7, wherein said secondary winding and said diode are connected in series.
9. A system as in claim 7, wherein said secondary winding and said diode are connected in series with each other as well as in series with the unit, and wherein said capacitor is connected across said diode in said secondary.
10. A system as in claim 9, wherein said diode is poled for producing easy current flow for discharge of said capacitor means when the unit discharges.
11. A system as in claim 10 wherein said transformer secondary is wound to cause said trigger capacitor to increase the magnitude of the voltage applied by said capacitor means to the unit.
1. A flash device, comprising a power source, a main capacitor charged by said power source, a discharge circuit for said main capacitor, a flash discharge tube which is provided in the discharge circuit, said discharge tube having a trigger electrode for triggering discharge, a diode in said discharge circuit, a transformer having a primary winding and having a secondary winding connected in series with the diode in the discharge circuit, a synchronizing contact switch connected to the primary winding for triggering said discharge tube, trigger means having a trigger capacitor and a trigger coil coupled with the trigger electrode, and an auxiliary capacitor connected in parallel with said diode and the secondary winding for charging during trigger operation to add to the magnitude of the voltage applied by said main capacitor to the discharge tube and for discharging during discharge of the discharge tube.
2. A flash device as in claim 1, wherein said trigger coil includes a primary winding and said synchronizing contact is connected in both the primary winding of the trigger coil and the primary winding of the transformer.
3. A discharge system for operating a flash unit from a power source, comprising discharge capacitor means for coupling across the power source, circuit means for coupling said capacitor means across the flash unit and for applying the voltage appearing at said capacitor means across the unit, triggering means to be coupled to said flash unit for applying a trigger pulse to the flash unit, said circuit means including a capacitor to be connected in series with the flash unit and control means coupled to said trigger means for charging the capacitor with a voltage that increases the magnitude of the voltage applied by said capacitor means across the unit, said control means including a path means for forming a discharge path for current through the unit, said path means including a diode.
4. A system as in claim 3, wherein the diode is poled for discharging current from said capacitor means when the flash unit discharges.
5. A system as in claim 3, wherein said control means includes a transformer coupled to said triggering means.
6. A system as in claim 3, wherein said control means includes a transformer coupled to said triggering means and said transformer has a secondary winding forming a part of said path means.
7. A system as in claim 6, wherein said path means includes a diode.
8. A system as in claim 7, wherein said secondary winding and said diode are connected in series.
9. A system as in claim 7, wherein said secondary winding and said diode are connected in series with each other as well as in series with the unit, and wherein said capacitor is connected across said diode in said secondary.
10. A system as in claim 9, wherein said diode is poled for producing easy current flow for discharge of said capacitor means when the unit discharges.
11. A system as in claim 10 wherein said transformer secondary is wound to cause said trigger capacitor to increase the magnitude of the voltage applied by said capacitor means to the unit.
Description:
The present invention relates to a flash device for a camera, and more particularly a flash device which can illuminate even when a terminal voltage of a main capacitor incorporated therein is lower than the lowest voltage enabling discharge of a flash discharge tube.
A flash device which is illuminated by discharging electric load stored in the main capacitor through a flash discharge tube does not flash when the terminal voltage of a main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
Therefore, in case of successive flash photographing when the main capacitor is not charged enough, or in cases when a close-up flash photography is taken with reduced illumination of the flash device when it is desired to use the flash device while the main capacitor is not fully charged, the conventional flash device has a defect that it does not illuminate.
An object of the present invention is to provide a flash device which can illuminate even when the terminal voltage of the main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
Another object of the present invention is to provide a flash device which is provided with means for giving additional voltage to the discharge tube when the terminal voltage of the main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
The present invention will be described by referring to the attached drawing.
The drawing shows one embodiment of a circuit diagram used in the flash device according to the present invention.
1 IS A POWER SOURCE CIRCUIT SUCH AS A DIRECT CURRENT BOOSTING CIRCUIT USING A TRANSISTOR-TYPE OSCILLATOR AND OTHER VARIOUS CIRCUITS. 2 IS A MAIN CAPACITOR USING A LARGE-CAPACITY CONDENSER. 3 IS A FLASH DISCHARGE TUBE, 4 IS A SECONDARY CAPACITOR USING A SMALL CAPACITY (FOR EXAMPLE, 0.001 - 0.0001μ F) condenser, 5 is a rectifying diode, 6 and 7 are respectively a boosting transformer and a condenser constituting a triggering circuit whose output charges the secondary capacitor. 8 and 9 are respectively a boosting transformer and a condenser of a triggering circuit which generates pulses for starting discharge of a discharge tube, 10 is a series transistor and 11 is a synchronizing contact.
The operation of the present invention device will be explained under.
When the switch (not shown in the drawing) of the power source circuit is made "on" the charge across the main capacitor is started and in a certain time the terminal voltage of the main capacitor reaches a prescribed value. Along with the charge across the main capacitor, the condensers 7 and 9 of the two triggering circuits are also charged through the series resistor 10. Under this condition, when the synchronizing contact 11 is made on, the electric loads of the condensers 7 and 9 of the triggering circuits pass to the boosting transformers 6 and 8 respectively and their secondary coils generate induced voltage. The induced voltage of the transformer 8 is added to the triggering electrode of the discharge tube 3 and induces the discharge. While the induced voltage of the transformer 6 is rectified by the diode 5 and passes to the secondary capacitor 4 and charges it into the polarity shown in the drawing. Namely the voltage charged across the secondary capacitor 4 and the terminal voltage of the main capacitor 2 are combined together and put to the both electrodes of the discharge tube. Therefore, even when the terminal voltage of the main capacitor 2 is lower than the lowest voltage for starting the discharge of the discharge tube, the discharge of the discharge tube can be started only if the combined voltage is higher than the lowest voltage. In this way, the moment the triggering pulse is put, the discharge tube starts the discharge and after then the illumination is effected by the electric load stored in the main capacitor.
The electric load stored in the secondary capacitor may be a small value, and its capacity is enough between about 0.001 and 0.01μF, and thus the time constant of the circuit can be shortened remarkably. And since the discharge current of the discharge tube flows through the secondary coil of the boosting transformer 6, it is necessary the impedance for this current is made low.
The device of the present invention operates effectively when it is used in a flash device using an automatic voltage control circuit, and has an advantage that the variable range of guide numbers is expanded.
A flash device which is illuminated by discharging electric load stored in the main capacitor through a flash discharge tube does not flash when the terminal voltage of a main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
Therefore, in case of successive flash photographing when the main capacitor is not charged enough, or in cases when a close-up flash photography is taken with reduced illumination of the flash device when it is desired to use the flash device while the main capacitor is not fully charged, the conventional flash device has a defect that it does not illuminate.
An object of the present invention is to provide a flash device which can illuminate even when the terminal voltage of the main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
Another object of the present invention is to provide a flash device which is provided with means for giving additional voltage to the discharge tube when the terminal voltage of the main capacitor is lower than the lowest voltage for starting discharge of the discharge tube.
The present invention will be described by referring to the attached drawing.
The drawing shows one embodiment of a circuit diagram used in the flash device according to the present invention.
1 IS A POWER SOURCE CIRCUIT SUCH AS A DIRECT CURRENT BOOSTING CIRCUIT USING A TRANSISTOR-TYPE OSCILLATOR AND OTHER VARIOUS CIRCUITS. 2 IS A MAIN CAPACITOR USING A LARGE-CAPACITY CONDENSER. 3 IS A FLASH DISCHARGE TUBE, 4 IS A SECONDARY CAPACITOR USING A SMALL CAPACITY (FOR EXAMPLE, 0.001 - 0.0001μ F) condenser, 5 is a rectifying diode, 6 and 7 are respectively a boosting transformer and a condenser constituting a triggering circuit whose output charges the secondary capacitor. 8 and 9 are respectively a boosting transformer and a condenser of a triggering circuit which generates pulses for starting discharge of a discharge tube, 10 is a series transistor and 11 is a synchronizing contact.
The operation of the present invention device will be explained under.
When the switch (not shown in the drawing) of the power source circuit is made "on" the charge across the main capacitor is started and in a certain time the terminal voltage of the main capacitor reaches a prescribed value. Along with the charge across the main capacitor, the condensers 7 and 9 of the two triggering circuits are also charged through the series resistor 10. Under this condition, when the synchronizing contact 11 is made on, the electric loads of the condensers 7 and 9 of the triggering circuits pass to the boosting transformers 6 and 8 respectively and their secondary coils generate induced voltage. The induced voltage of the transformer 8 is added to the triggering electrode of the discharge tube 3 and induces the discharge. While the induced voltage of the transformer 6 is rectified by the diode 5 and passes to the secondary capacitor 4 and charges it into the polarity shown in the drawing. Namely the voltage charged across the secondary capacitor 4 and the terminal voltage of the main capacitor 2 are combined together and put to the both electrodes of the discharge tube. Therefore, even when the terminal voltage of the main capacitor 2 is lower than the lowest voltage for starting the discharge of the discharge tube, the discharge of the discharge tube can be started only if the combined voltage is higher than the lowest voltage. In this way, the moment the triggering pulse is put, the discharge tube starts the discharge and after then the illumination is effected by the electric load stored in the main capacitor.
The electric load stored in the secondary capacitor may be a small value, and its capacity is enough between about 0.001 and 0.01μF, and thus the time constant of the circuit can be shortened remarkably. And since the discharge current of the discharge tube flows through the secondary coil of the boosting transformer 6, it is necessary the impedance for this current is made low.
The device of the present invention operates effectively when it is used in a flash device using an automatic voltage control circuit, and has an advantage that the variable range of guide numbers is expanded.